Application of frequency correlation function to radar target detection

Abstract

Analysis of high-resolution 35 GHz synthetic aperture radar (SAR) imagery of terrain reveals that when point targets, such as vehicles, are viewed at angles close to grazing incidence, they are often difficult to distinguish from tree trunks because the radar cross section (RCS) intensities of the vehicles are comparable to the upper end of the RCS exhibited by tree trunks. To resolve the point target/tree trunk ambiguity problem, a detailed study was conducted to evaluate the use of new detection features based on the complex frequency correlation function (FCF). This paper presents an analytical examination of FCF and its physical meaning, the results of a numerical simulation study conducted to evaluate the performance of a detection algorithm that uses FCF, and the corroboration of theory with experimental observations conducted at 35 and 95 GHz. The FCF-based detection algorithm was found to correctly identify tree trunks as such in over 90% of the cases, while exhibiting a false alarm rate of only 3%.

Synthetic Aperture Radar Correlation Imaging

“…The first body of literature [26,24,25,27,5,9] seeks to take advantage of what is known as the memory effect of scattering of waves by random media. The angular correlation function and the memory effect.…”

SAR correlation imaging and anisotropic scattering

“…Correlation imaging is of interest because it has been shown to improve resolution, reduce sidelobes, and minimize the effects of clutter scatterers on the final image [34,42,43,40,41,7,14]. Note clutter is a term often used in the SAR literature to describe scatterers present in the imaging scene which are not of interest.…”

“…The most relevant literature to this current study [42,43,40,41,7,14] seeks to make use of the memory effect of scattering of waves by random media or scatterers to minimize the effects of clutter in electromagnetic imaging applications. The memory effect [16,20] states that the angular correlation function (ACF) of optical waves scattered by random media is only nonzero along a memory line (for rough surface scattering) or memory dots (for volume scattering).…”

“…It is argued in [42,43,40,41,7,14] that this effect holds for electromagnetic waves as well and that by avoiding the inclusion of the memory line or dots in the data one is able to decrease the effect of clutter on an image formed from electromagnetic scattered field data. The angular correlation function is given as follows: (1) Γ(k s1 ,k i1 ;k s2 ,k i2 ) = F (k s1 ,k i1 )F * (k s2 ,k i2 )…”

“…In [42,43,40,41,7,14] it is argued this method reduces clutter effects on radar images specifically for both volume scatterers and rough surfaces. The author's previous work [34] aimed to study the ability of a correlation imaging algorithm which avoided the memory directions to minimize the effects of vegetation-like clutter in SAR imaging.…”